Oxidation of hydrocarbons



Nov. 5, 1963 s, ox ETAL I 3,109,864

"y OXIDATION OF HYDROCARBONS Filed Sept. 26. 1961 NON-CONDENSIBLES 2 r15PHASE 9 couosnssn SEPARATOR I wA'rR ACTING 'q owsa HOT Ll Ul '6 mono 0N+0 CONTAINING GAS REACTOR. vAPoRs 1 OXIDATION REACTOR. 5

LIQUID REACTION 7 MIXTURE D 3* WM INVENI ORS SHERWOOD M FOX JOHN WCOLTON ATTORNEY United States Patent Filed Sept. 26, 1961, Ser. No.140,794

6 Claims. (11]. 260-631) This invention relates toa new and improvedprocess and apparatus for the oxidation of hydrocarbons. Morespecifically, this invention teaches a process and apparatus forovercoming many difficulties hitherto unavoidable in hydrocarbonoxidation. Still more particularly, the instant invention describesmeans for overcoming problems in hydrocarbon oxidation wherein boroncompounds are utilized to obtain the desired oxidation product.

In hydrocarbon oxidation the presence of water often interferes with thesuccessful conversion to the desired reaction product. This water isformed by the oxidation reaction per se or introduced into the reactorfrom external sources.

One technique known to the prior art for removing water from the reactoris to withdraw it as a vapor along with unreacted vaporized hydrocarbonsand non-condensible gases. The total of these vapors, known as boil-uare subsequently cooled; the water and hydrocarbons are condensed andsettled; the water phase and the hydrocarbon phase are separated; andthe water is discarded and the hydrocarbon is recycled to the reactor.Boil up rate is determined by many factors, such as the temperature andpressure of the reactor.

It has been found that the aforementioned procedure suffers from manydisadvantages which make the overall process much less efiicient andeconomically attractive.

Firstly, in order to separate the boiled up hydrocarbons and water it isnecessary that they be cooled and condensed. Upon recycling the coldhydrocarbons, it becomes necessary to add large amounts of heat to thereactor to maintain proper reaction conditions.

Secondly, the condensation of the vaporous hydrocarbons requires theremoval of large quantities of heat and sizable condensing surfaces.Such factors additionally increase the cost of the process.

Thirdly, even at the low temperature employed in the separation of thehydrocarbon-water condensate, complete removal of the water from thehydrocarbon phase is extremely difiicult. This difiiculty arises becauseof the presence of materials, perhaps surface active reaction products,which emulsify a portion of the water (referred to herein as phasedwater) with the hydrocarbon phase.

In accordance with this invention, it has been found that theaforementioned difficulties can be overcome by direct- 1y contacting thereactor boil-up vapors with the hydro carbon phase from the phaseseparator prior to recycle to the reactor.

This invention is particularly important in hydrocarbon oxidationprocesses where boron compounds such as meta boric acid are added to thereactor mass in order to modify the extent of the oxidation reaction.This is true because the presence of even small quantities of waterdestroys the efiect of the added boron compound. For a completedisclosure of such reactions and the detrimental efiect of water see US.application Ser. No. 85,987 filed January 31, 1961. A wide variety ofhydrocarbons may be oxidized according to the process and apparatus ofthe instant invention. Particularly applicable are lower molecularweight hydrocarbons having from 2 to carbon atoms per molecule,preferably from 3 to 8. They may be either cyclic or acyclic compoundssuch as straight or branched chain paraifins including butane, penta-ne,methyl butane, etc. Particularly preferred are cycloalkanes such ascyclohexane.

The attached FIGURE is a schematic flow sheet illustrating theinvention.

The batch oxidation reactor .1, which is charged with 308 parts of metaboric acid and 2711 parts of cyclohexane, is maintained at a temperatureof about 330 F. and a pressure of 120 psig. Air is introduced into thereactor 1 through line 5 and about 77 parts of 0 absorbed. About 8% ofthe cyclohexane reacts and the liquid reaction mixture Withdrawn throughline 6. This reaction mixture is treated to recover the product in anydesired manner, such as that disclosed in the aforementioned patentapplication. Heat is supplied to the reactor through means 7 in aconventional manner. A high boilup is maintained and the vapors removedfrom the reactor through line 8 contain about 3200 parts of cyclohexane,63 parts of water and 254 parts of nitrogen. These vapors, at atemperature of about 330 F., are passed to the contacting tower 2. Thistower may be a spray tower, packed column or other conventionalapparatus. In the contacting tower 2, the hot vapors are brought intodirect contact with cold recycle liquid cyclohexane containing phasedwater. This latter stream, containing about 1500 parts of cyclohexaneand about 15 parts phased water, enters the contacting tower 2 throughline 9 at a temperature of about F. The contact of the two streamsresults in (l) the condensation of about 1500 parts of cyolohexane andthe cooling of the remaining vapors; (2) the heating of the cyclohexaneliquid to about 310 F. and (3) the stripping out of the phased waterfrom the liquid recycle stream. The heated cyclohexa-ne stream iswithdrawn from the contacting tower 2 through line 1%) and containsabout 3000 parts of essentially water free cyclohexane. This stream ispassed back to the oxidation reactor 1 wherein it may undergo furtherreaction. The cooled vapors (containing 1700 parts of cyclohexane, over70 parts of water, and 254 parts of nitrogen) leave the top of thecontacting tower 2 through line 13, and pass to condenser 3 whereinessentially all of the cyclohexane and water are condensed.Non-condensable gases, e.-g. nitrogen, are removed via line 14. Thisstream contains about 200 parts of cyclohexane vapor which may berecovered in a subsequent scrubbing operation. Through line 15, thecyclohexanewater condensate, at a temperature of about 100 F., passes tophase separator 4-. About 63 parts of water are removed from the bottomof the separator 4 through line 16 as the water phase and discarded.About 1500 parts of cyclohexane containing phased water are removed vialine 9 and processed as previously described.

The above example is illustrative of the invention only and is notintended to be definitive thereof. Many modifications are within thespirit of the instant invention.

For example, the cyclohexane stream line 10 may be heated in order toreduce the heat requirements through line 7.

The non-condensible stream leaving the condenser 3 through line 14 maybe recycled to the reactor. Such procedure is particularly advantageouswherein oxygen concentrations less than that of air are desirable.

The temperature prmsures and flow rates to the various units describedabove may be readily selected by those skilled in the art. Theseconditions are dependent on such factors as the particular hydrocarbonundergoing reaction, the amount of oxygen feed to the reactor, theamount of boil-up, and efliciency of the contacting tower and condenser.

It will be understood that modifications and variations may be effectedwithout departing from the spirit of the invention.

We claim:

1. A new and improved process for the oxidation of hydrocarbons whichcomprises: reacting said hydrocarbon with a molecular-oxygen containingvgas in an oxidation zone; withdrawing a gaseous eiiluent containingunreacted hydrocarbon and water; intimately contacting said gaseousefiluent with a relatively cool liquid stream of said hydrocarbons;condensing a portion of said hydrocarbon from said gaseous efl'luent insaid liquid stream; introducing said condensed hydrocarbon and saidliquid hydrocarbon into 'said oxidation zone; withdrawing the remaininguncondensed hydrocarbon and water; condensing the remaining uncondensedhydrocarbon and water in said gaseous efiiuent; separating saidcondensed water and hydrocarbon; and recycling said last mentionedcondensed hydrocarbon as the aforesaid relatively cool liquid stream.

2. The process of claim 1 wherein said hydrocarbon is a cyoloalkane.

3. The process of claim 2 wherein said cycloailkane is cyclohexane.

4 4. The process of claim 1 wherein said hydrocarbon is reacted withsaid molecular oxygen containing gas in the presence of a boroncompound.

5. The process of claim 4 wherein said boron compound is meta boricacid.

6. The process of claim 1 wherein said relatively cool liquid stream ofhydrocarbons contains phased water. :1

References Cited in the file of this patent UNITED STATES PATENTS2,576,078 Pelton Nov. 20, 1951 2,863,737 Green Dec. 9, 1958 2,884,444Groszos Apr. 28, 1959 2,929,690 Bennett et al Mar. 22, 1960 2,938,924Simon et al May 31, 1960' M ii

1. A NEW AND IMPROVED PROCESS FOR THE OXIDATION OF HYDROCARBONS WHICHCOMPRISES: REACTING SAID HYDROCARBON WITH A MOLECULAR-OXYGEN CONTAININGGAS IN AN OXIDATION ZONE; WITHDRAWING A GASEOUS EFFLUENT CONTAINIGUNREACTED HYDROCARBON AND WATER; INTIMATELY CONTATING SAID GASEOUSEFFLUENT WITH A RELATIVELY COOL LIQUID STREAM OF SAID HYDROCARBONS;CONDENSING A PORTION OF SAID HYDROCARBON FROM SAID GASEOUS EFFLUENT INSAID LIQUID STREAM; INTRODUCING SAID CONDENSED HYDROCARBON AND SAIDLIQUID HYDROCARBON INTO SAID OXIDATION ZONE; WITHDRAWING THE REMAININGUNCONDENSED HYDROCARBON AND WATER; CONDENSING THE REMAINING UNCONDENSEDHYDROCARBON AND WATER IN SAID GASEOUS EFFLUENT; SEPARATING SAIDCONDENSED WATER AND HYDROCARBON AS THE AFORESAID RELATIVELY COOL LIQUIDSTREAM.
 4. THE PROCESS OF CLAIM 1 WHEREIN SAID HYDROCARBON IS REACTEDWITH SAID MOLECULAR OXYGEN CONTAINING GAS IN THE PRESENCE OF A BORONCOMPOUND.